A Direct Current-Direct Current (DC-DC) converter can operate by voltage mode control or current mode control depending on its feedback scheme. The current mode control scheme is one of switch mode power supply control systems that are usefully applied. Advantageously, the current mode control makes it possible to realize a simple system compensation circuit. For example, compensation can be implemented with a single compensation capacitor and resistor. Accordingly, system characteristics can be achieved to the same effect as operating as a system having one pole. Other advantages with the current mode control are excellent characteristics of line regulation that is the capability of maintaining a constant output voltage despite changes to an input voltage, and good noise immunity.
However, a system having a duty ratio exceeding 50% for a Pulse Width Modulation (PWM) signal needs a linear or non-linear circuit. This is called a slope compensation circuit. The additional use of a slope compensation circuit can prevent sub-harmonic oscillation.
FIG. 1 is a block diagram of DC-DC converter 100 that operates in a current mode control scheme.
As illustrated in FIG. 1, DC-DC converter 100 includes slope compensation circuit 110 for slope compensation.
FIG. 2A illustrates an inductor (L) current in a DC-DC converter without a slope compensation circuit and FIG. 2B illustrates an inductor (L) current (IL) in a DC-DC converter with a slope compensation circuit. A solid line represents an ideal inductor current and a dotted line represents a real inductor current.
As illustrated in FIGS. 2A and 2B, the DC-DC converter with a slope compensation circuit demonstrates a stable inductor waveform.